How did an obscure film titled either "Innocence of Muslims" or "The Real Life of Muhammed" lead to the emotional and violent ramifications playing out now in Egypt, Libya, Tunisia and other places in the Muslim world?
It was first posted on YouTube by a user called "sam bacile" in July 2012, and has to date received about 450,000 views.
The trailer began to receive more attention this month. On September 4, the same user posted a version dubbed in Arabic, which has since garnered tens of thousands of views.
Morris Sadek, an Egypt-born Coptic Christian who lives in the US, told the Associated Press he had been promoting the film on his website. He also tweeted a link to the trailer on September 9.
Sadek, who serves as head of the National American Coptic Assembly, is known for his vehemently anti-Islam views. He told the Wall Street Journal that "the violence that it [the film] caused in Egypt is further evidence of how violent the religion and people are".
Terry Jones, the Florida pastor whose burning of copies of the Quran in 2011 spurred riots across the Muslim world leading to several deaths, also reportedly promoted the film.
The Arabic version of the trailer received heavy media coverage in Egypt last week, including by controversial hardline TV host Khaled Abdallah, who reported on the film on September 8.
A clip of the show was posted to YouTube on September 9, where it has received almost 400,000.
"The operation behind this film appears to be extreme Egyptian Copts who want to discredit the Morsi government and create a provocation," journalist Max Blumenthal told Al Jazeera on Wednesday.
"They oppose the revolution and are aligned with Christian right groups who have an apocalyptic, theocratic agenda and who are inciting against Muslim-Americans," Blumenthal said.
"They put Muslims in the US in danger, they put Copts in Egypt in danger, and they're putting US diplomats in danger."
YouTube clip blocked
The Afghan government on Wednesday temporarily blocked YouTube in an effort to discourage people from watching the clip. YouTube also blocked the video in Egypt, according to news agency reports.
In a statement issued on Wednesday,YouTube said: "We work hard to create a community everyone can enjoy and which also enables people to express different opinions. This can be a challenge because what's OK in one country can be offensive elsewhere.
"This video, which is widely available on the web, is clearly within our guidelines and so will stay on YouTube. However, given the very difficult situation in Libya and Egypt we have temporarily restricted access in both countries.
"Our hearts are with the families of the people murdered in [Tuesday's] attack in Libya."
Observers say Google has grown more averse to removing videos. After acquisition of YouTube in 2006, it was accused of censorship in several high-profile controversies.
"They're squeezed on all sides," said Rebecca MacKinnon, a fellow at the New America Foundation. "But because of pressure from a lot of people who feel they made the wrong decisions, they now generally err on the side of keeping things up."
In recent years, Google has used technology to filter out videos in certain countries to comply with local regulations.
The trailer for the film has been cited as the cause for riots at US diplomatic posts in Egypt and Libya.
Even so, the existence of the purported filmmaker, Sam Bacile, allegedly a 52-year-old Israeli-American real estate developer, has yet to be proven.
In interviews with the AP and the Wall Street Journal, a man calling himself "Sam Bacile" said he had raised about $5m to produce the film. He also was quoted describing Islam as "a cancer", and claimed he had raised money from "about 100 Jewish donors" to make the video.
The interview subject did not give the same age during his two known press interviews. He told the AP he was 56.
The man said the amateur, two-hour-long film had involved dozens of actors and was produced in California in 2011. New reports found no prior social media presence by the director or any International Movie Database page for the film.
In an interview with the AP, Nakoula Basseley Nakoula, a 55-year old Coptic Christian from California said he was involved in the production of the film, but that he did not direct it.
Although Nakoula denies he is the same person as "Sam Bacile", the cell phone number used to call "Bacile" was traced to an address near Los Angeles where the AP found Nakoula.
Nakoula has also reportedly used several aliases, including Nicola Bacily and Erwin Salameh.
In 2010, he pleaded no contest to charges of bank fraud in California. He was sentenced to 21 months in prison and ordered to pay more than $790,000 in restitution.
The director of the California Film Commission, which issues permits for films that are shot in the state, told the Huffington Post that no permit was ever granted to anyone by the name "Sam Bacile".
The trailer for the film, the full version of which is so far unavailable to the public, portrays Islam’s Prophet Muhammad as a fraud and a womaniser, and depicts him having sex. The entire film has only been shown once in public, at a theatre in Hollywood, said the source who identified himself as Bacile.
He also explained he made the film because “after 9/11 everybody should be in front of the judge. Even Jesus, even Muhammad", according to the AP.
Actors who participated in the filming have emerged to say they had no idea the film was even about Muhammad or Islam. The original casting call was reportedly for a film called "Desert Warrior" by director Alan Roberts.
Reports indicate that all the film's religious references were actually dubbed after the original shooting.
Bacile is now reportedly in hiding. Reports suggest the name is merely cover for a larger group, or a pseudonym for someone who may be neither Israeli nor Jewish, but who cited such an identify to inflame sectarian tensions.
One of the actresses who says she was tricked into being in the film says Bacile told her on set that he was Egyptian, and that he spoke Arabic to other men present.
Reuters has reported that Egypt's Coptic Orthodox church issued a statement condemning some Egyptian Christians living aboard who it said had financed "the production of a film insulting Prophet Muhammad".
In Egypt and Libya, public anger at the video spilled over on Tuesday, leading to the death of the US ambassador in Benghazi, Libya and the evacuation of embassy workers in Cairo.